Rheostat



Patented June 18, 1935 UNITED STATES PATENT OFFICE RHEOSTAT Henry J.Bertram, Kansas City, Mo.

Application April 21, 1932, Serial No. 606,587

1 Claim. (Cl. 201-51) This invention relates to electromotive forcetrollable knob 8 must be within easy reach of generating apparatus andis especially designed the driver of the automobile and suitable con tobe built into and combined with generating nections must be made to theattachment apparatus for automobiles, and the primary obthrOughgrounding Said instrument board and ject of the invention is theprovision of a variable ny necessary W leads "I, w y to connect 5resistance element for such generating equipin series the resistancedevice with the shunt ment which may be associated with the shuntcircuit of the nera or circuit of a shunt-wound generator. The deviceitself may be constructed to include One of the objects of thisinvention is to probody ll, cored out to create cavity l5 to form a videa manually controllable, variable resistance housing for a Series O plas W ich a e 10 element that may be associated with the charggroupedtogether Within y and insulated ing apparatus for automobiles andpositioned on therefrom y lining IT s illustrated in the instrumentboard within easy reach of the Plates e o med of material havingdifdriver, and which may be manipulated to vary en o du ve p pe a thegroup of the electromotive force output as the speed of plates I6 isengaged at its one Side y a Spring 15 the automobile or contemplatedlength of a trip analogous yieldable member While the is changed. otherside of the group of plates is engaged by It is known that the ordinarycharging appaknob ratus for automobiles is equipped with means p fi a y,sc ew-th eaded Shank of knob 20 whereby the out ut thereof to thestorage bat- 8 actually bears in t ne sid of h r p of 20 tery might bealtered by adjusting certain parts Plates '6- Tllrning knob 8 and Shank3 in the and by having one skilled in th busi ss t dappropriatedirection causes a movement toward just parts of the generator which maybe reached and from the group of plates a d this e 'fl through the useof special equipment. It is also compresses or allows p n i n the p of 5known that over-charging sometimes occurs Spring Set p a greater lesserpressure 5 when long trips are taken and it becomes necesto holdtogether the plurality of plates sary at such times to burn the lightsof the autoh per ion above set down causes the series mobile to precludesuch action and its dangerous of p s to v y their Conductive P p y,results. and when the same are included in an electrical 30 Thisinvention contemplates the use of a novel u the pressure ng them toether (16- 30 attachment operable from the drivers seat, termines theamount of resistance which they set which is connected in series withthe aforemenup in said circuit. tioned shunt circuit, having plates ofdifferent V y has a de diameter Sufiiciently conductive properties andmeans to vary the greater than the diameter of plates Hi to allowpressure holding together said plates. clearance when insulating liningl! is in place. 35

The advantages of such an attachment are These parts of the device areinserted through obvious and with the foregoing general objects the openend of body M as is spring l8 and a in view, the specific form andstructure of a disk 2|. After assembly, ring 23 may be posipreferredembodiment of the invention will now tioned through the medium ofappropriate WWW a'zmr D f mew-threads. Ring 23 is of insulating matei 1in) in Unti /EV W001i! ,0 tlll'ltlt flllll] ,JtSSlHl-T Since knob 8 andshank 20 are not functioning when this setting takes place, any movementon their part after setting will place greater pressure against plates[6 and gradually increase the output of electromotive force rather thanever decreasing the same from the said predetermined minimum output.After installation screw 25 need never be adjusted.

A shunt-wound generator I2 is diagrammatically illustrated in Fig. 4,and a movable brush 22 is likewise shown to establish the possibility ofaltering the electromotive force output of generator l2 to suit therequirements of the particular make of automobile with which thegenerating apparatus is associated. After movable brush 22 is set and afurther setting of the device here contemplated, to insure a minimumoutput by generator I2, is made, the owner of the automobile alters theelectromotive force input to storage battery 24 by merely manipulatingthe attachment at the instrument board.

As illustrated in Fig. 4, the attachment is connected in series with theshunt circuit of generator l2, the resistance of which is varied tochange the generator output. That is to say, when the resistance of theshunt circuit is altered, output from generator l2 through the externalcircuit is altered in accordance with the change in the resistance ofthe shunt circuit. An ammeter 26 is usually interposed in the externalcircuit of the generating apparatus, through which passes the charge,whereby to indicate to the driver the output strength of generator l2.In the type of generator illustrated, there are two stationary brushes28 and 30 respectively, the latter of which is attached to any suitableground 32 by wire 34. A conductor 36 leads from stationary brush 28 toammeter 26, and suitable wires or other conducting means 38 join ammeter26 and storage battery 24. The external circuit is completed byconnection 40 which joins battery 24 to ground 32.

The two shunt-wound field magnets 42 form a part of generator l2 and arejoined by conductor 44 in the well known manner. Stationary brush 30 andwire 34 combine with movable brush 22, field magnets 42, and theirconnecting conductor 44, wire 10 and, again, ground 32, to set up thecomplete shunt circuit, within which is interposed the variableresistance attachment hereinbefore described.

The external circuit forming a part of the charging apparatus is quicklyfollowed by referring to Fig. 4, and may be established from ground 32back to ground 32 as follows: Wire 34 to fixed brush 30 of generator l2,fixed brush 28 to conductor 36, through ammeter 26 to conducting means38, to battery 24, and thence to connection 40 which leads to ground 32.

Operation of generating apparatus such as set down herein is very wellknown. The same has been described merely to render clear the exactcombination which is set up when a variable resistance attachmentcontemplated by this invention is used therewith.

Materials from which plates l6 are made need not be of a specific kind,so long as the conductive properties of the plates forming the group aredifierent and so long as the pressure exerted upon plates I6 causes avariation in the resistance which they establish in the shunt circuit.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

A rheostat of the character described comprising a body having a cavityformed therein; internal threads formed in the body wall adjacent oneend thereof; an externally and internally threaded portion of reduceddiameter at the other end of said body whereby to form an annularshoulder on the body; a manually operable control knob having a threadedshank in engagement with the internal threads of the portion of reduceddiameter; a threaded collar of insulating material having a screwadjustably carried thereby closing one end of said body in opposedrelation to the said threaded shank; a plurality of superimposed platesof different electrical conductive properties positioned in a' pile insaid cavity between the said manually operable control knob shank andthe said screw: and a compression spring between two of said disks ofthe'pile, the said reduced portion of said body having a nut inscrewthreaded engagement therewith for movement toward and from the saidannular shoulder whereby to secure a support therebetween to hold therheostat in operative position.

HENRY J. BERTRAM.

